1. Field of the Invention
This invention relates to a method for archiving documents on a personal computer by providing an acquisition and reproduction circuit for activating the memory of a personal computer to store a binary image identical of the last printed document output signal from an attached printer.
2. The Prior Art
It is known that a copy of a document or of a drawing is produced by making a photostatic copy. The methods used in this connection are mainly:
(a) Filming, e.g. microfilm; or
(b) Screened electronic copy by a copier or scanner, such as defined by JP 2-246469 (A).
Both methods are based on acquisition of the original by mechanically passing it through an optical lens system. The limitations resulting from this method are, on the one hand, lack of speed of such systems, and possible falsification due to soiling or damage of the lens system, on the other hand.
Scanning images can be made by scanning the data carrier, i.e., the printed page. In this case, the page has to be printed before scanning can occur. Optical scanners can be used to monitor the printed image after the printing process and prepare the result in a digital format, i.e., for archiving purposes. The electronic copy produced by a scanner is stored in a memory so as to be available for repeated printouts.
Scanning images can also be done by scanning the printers bitmap memory. In this case, the page is not printed before scanning. In this case, it is necessary to have additional information on how and where the contents for the printer's bitmap memory has to be organized to represent the human readable text image. This can be done by reading an interpreting the commands in the printer's specific printer command language, etc. and then providing the printers' bitmap memory with additional address lines to get the raster information out of the printer's bitmap memory for copying purposes. If this is done correctly, the result should be the image like the printer's printing engine would have printed.
Raster based printers put images on the paper by transferring raster data to a printing drum which is rotating. If one is monitoring only the raster data transferred to the printer's drum without any additional information, there is not exact possibility to make a decision where to place the raster data to compose an image which is the same as the image on the printer's raster drum, and one turn around later, on the paper.